Given the contribution of uncontrolled inflammation to many human diseases, the identification of endogenous control mechanisms in the acute inflammatory response is of wide interest (1). Classic lipid mediators such as the prostaglandins and leukotrienes are well appreciated for their important pro-inflammatory roles in inflammation (2). In recent years, the resolution of inflammation has emerged as an area with considerable potential to contain local mediators that may be useful for new therapeutic approaches (for reviews, see 3, 4). Using an unbiased systems approach employing lipidomics, proteomics and cell trafficking to study self-resolving inflammatory exudates revealed that the termination of acute inflammation involves active biosynthetic processes producing novel endogenous lipid mediators that are both anti-inflammatory and pro-resolving (5-8). It is now clear that resolution of acute inflammation is an active rather than passive process as previously understood (9), generating novel potent counter-regulatory mediators termed resolvins and protectins (for a recent review, see Ref. 4).
Resolvins and protectins are biosynthesized by exudates from essential omega-3 fatty acids (e.g., EPA and DHA), and the structures are established for key members of these families (4). The immune regulatory actions of omega-3 fatty acids and their roles in human health and diseases such as cancer and neuroinflammation are widely appreciated (10-12). Although omega-3 fatty acids are in wide use as dietary supplements and potential therapeutics in many diseases including inflammatory diseases, their mechanism(s) and connection to inflammation remain of interest. Resolvins and protectins display potent multi-level anti-inflammatory and pro-resolving actions (13) and are members of a new genus of endogenous mediators of resolution (4). For example, resolvin E1 is biosynthesized from EPA and interacts with specific receptors to control inflammatory cells (14, 15). Also, fat-1 transgenic mice, producing higher endogenous levels of omega-3, show reduced inflammatory status and elevated levels of resolvins and protectins, which when administered reduce inflammation and stimulate resolution (16-18). The main biosynthetic route with DHA for resolvins and protectins proceeds during resolution via a 17S-hydroperoxydocosahexaenoic intermediate produced by a lipoxygenase mechanism. With aspirin therapy, acetylated cyclooxygenase-2 produces aspirin-triggered 17R-epimers of resolvins and protectins as well as enhances their formation (6). Genetic deficiency or overexpression of murine 12/15-LOX regulates production of resolvins and protectins and alters their responses to both thermal injury and extent of atherosclerosis (17, 18).
Therefore, a need exists for a further understanding of, an exploration or and identification of new useful materials previously not appreciated as potent biological mediators of interest.